JPH11278855A - Quartz glass crucible for pulling up silicon single crystal and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve single crystallization ratio by imparting a specific compressive stress to a transparent layer of a crucible composed of the transparent layer on the inner surface side and an opaque layer, which is on the outer periphery of the transparent layer and in which many bubbles are present, to suppress the incorporation of the bubbles into a silicon melt. SOLUTION: The crucible is formed from the 2 layers and has the transparent layer 3 on the inner surface side 2 and the opaque layer, which has many bubbles, for example about 8000-12000/cm<3> bubbles having 1.0-250 μm particle diameter and 32-38 MPa breaking strength, on the outer periphery of the transparent layer 2. The compressive stress 30-50% of the rupture strength of the opaque layer 5 is imparted to the transparent layer 2. The thickness of the transparent layer 3 is controlled to >=1 mm and >=60% of that of the opaque layer 5. As a result, micro-bubbles existing in the transparent layer 3 expands to large bubbles and the incorporation of the bubbles to a molten silicon with the dissolution of the transparent layer 3 of the inner surface side 2 is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a quartz glass crucible for pulling a silicon single crystal and a method of manufacturing the same, and more particularly to a quartz glass crucible capable of obtaining a high yield of pulling a silicon single crystal and a method of manufacturing the same.

[0002]

2. Description of the Related Art A silicon single crystal used for a substrate of a semiconductor device is generally manufactured by a Czochralski method (CZ method). In the CZ method, a polycrystalline silicon raw material is loaded into a quartz glass crucible and loaded. The obtained silicon raw material is heated and melted from the surroundings, and the seed crystal suspended from above is brought into contact with the silicon melt and then pulled up.

Conventionally, a crucible for the CZ method has a transparent layer on the inner surface side and an opaque layer on the outer periphery of the transparent layer.
A layer of quartz glass crucible is used.

In the opaque layer, there are about 8000 to 12000 bubbles / cm 3 having a diameter of 10 to 250 μm.
It is apparently opaque, and this opaque layer serves to uniformly transfer heat from a heater arranged on the outer periphery of the crucible to the silicon melt in the crucible.

On the other hand, in the transparent layer, efforts have been made to eliminate air bubbles in this layer, but at this stage, complete elimination has not been achieved, and 0.05 to 0.5 volume At present, about% of bubbles remain.

[0006] For example, even if no bubbles are confirmed by observation with a microscope, there are still some that become bubble nuclei. When silicon single crystal is pulled and heat is applied to the quartz crucible, bubbles are generated from these bubble nuclei. The bubbles are formed, and the bubbles are mixed into the silicon melt together with the dissolution of the transparent layer on the inner surface side. The bubbles are taken into the silicon single crystal being pulled up, causing crystal defects (dislocations) due to crystal dislocations. There is a problem that this is a factor that lowers the conversion rate (DF rate).

As described above, the yield of pulling a silicon single crystal by the CZ method is greatly affected by the quality of the quartz glass crucible, and particularly affected by the presence of bubbles on the inner surface of the quartz glass crucible.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a quartz glass crucible capable of obtaining a high yield of pulling a single crystal without lowering the DF ratio and a method of manufacturing the same.

[0009]

Means for Solving the Problems In order to achieve the above object, the invention of claim 1 of the present application has an opaque layer having a transparent layer on the inner surface side and having a large number of bubbles around the transparent layer. In a quartz glass crucible formed of two layers having
The gist is a quartz glass crucible for pulling a silicon single crystal, wherein the transparent layer has a compressive stress of 30 to 50% of the breaking strength of the opaque layer.

According to a second aspect of the present invention, there is provided a quartz glass crucible for pulling a silicon single crystal according to the first aspect, wherein the opaque layer has a breaking strength of 32 to 38 MPa.

According to a third aspect of the present invention, the thickness of the transparent layer is at least 1 mm, and the thickness of the transparent layer is 60% or less of the thickness of the opaque layer. It is a gist of a quartz glass crucible for pulling a silicon single crystal.

According to a fourth aspect of the present invention, there is provided a crucible mold in which a quartz powder is filled in a crucible-like body, and a quartz glass crucible for pulling a silicon single crystal which is heated from the inner side of the crucible-like body. In the manufacturing method, it is a method of manufacturing a quartz glass crucible for pulling a silicon single crystal, wherein cooling conditions are changed between an inner surface side and an outer surface side of the quartz glass crucible after heating the crucible forming mold. .

According to a fifth aspect of the present invention, after the heating of the quartz powder is completed, an inert gas is introduced into an inner surface region of the quartz glass crucible and forced cooling is performed from the inner surface side. The gist is to provide a method for manufacturing a quartz glass crucible for pulling a silicon single crystal.

The invention of claim 6 of the present application is characterized in that the flow rate of the inert gas is 100 to 300 liter / min, the forcible cooling time is 5 to 10 minutes, and then the cooling is performed. Item 5 is a method for manufacturing a quartz glass crucible for pulling a silicon single crystal according to Item 5.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a quartz glass crucible according to the present invention and a method for manufacturing the same will be described below with reference to the accompanying drawings.

FIG. 1 shows a quartz glass crucible 1 according to the present invention.
A transparent layer 3 on the inner surface 2 of the quartz glass crucible 1;
The quartz glass crucible 1 is formed of two layers having an opaque layer 5 having bubbles on the outer surface 4 thereof.

The opaque layer 5 is apparently opaque with bubbles having a diameter of 10 to 250 μm of about 8000 to 12000 bubbles / cm 3 and has a breaking strength of 32 to 38 MPa.

The transparent layer 3 has a breaking strength of 30 of the opaque layer 5.
It has a compressive stress of about 50%, contains bubbles of about 0.05 to 0.5% by volume substantially, and has bubble nuclei that cannot be confirmed by microscopic observation.

The thickness of the transparent layer 3 is at least 1 mm, and the thickness of the transparent layer 3 is 6 times the thickness of the opaque layer 5.
0% or less.

When the compression pressure of the transparent layer 3 is changed to the opaque layer 5
When the breaking strength of the transparent layer 3 is less than 30%, the expansion of the bubbles in the transparent layer 3 or the bubbles generated from the nuclei of the bubbles and the dissolution of the transparent layer 3 on the inner surface 2 cannot suppress the incorporation of the bubbles into the silicon melt. In addition, the bubbles in the opaque layer 5 expand and expand toward the transparent layer 3 and rupture, adversely affecting the growth of the silicon single crystal,
The DF rate cannot be prevented from lowering.

If it exceeds 50%, the quartz glass crucible 1 may be broken due to the thermal stress applied to the quartz glass crucible 1 when the single crystal is pulled or the load of the molten silicon 6 loaded in the quartz glass crucible 1.

The breaking strength of the opaque layer 5 is 32 to 38 MPa.
It is necessary for the quartz crucible to be structurally.

When the thickness of the transparent layer is less than 1 mm, the thickness required for ordinary service becomes no more than 1 mm due to erosion of the inner surface of the crucible by silicon melt which is inevitable during pulling of the single crystal. is there. When the thickness of the transparent layer exceeds 60% of the thickness of the opaque layer, 30 to 50% in the transparent layer
% Of the compressive stress, the holding strength of the opaque layer becomes insufficient.

Next, a method for manufacturing a quartz glass crucible according to the present invention will be described with reference to the drawings.

The crucible forming die 8 of the manufacturing apparatus 7 as shown in FIG. 2 is composed of a gas permeable member such as a die having a plurality of through holes or a highly purified porous carbon type. Inner member 9 and the ventilation portion 1
0 and a holding body 11 for holding the inner member 9.

A rotating shaft 12 connected to rotating means (not shown) is fixed to a lower portion of the holding body 11, and is supported so as to be rotatable together with the crucible forming die 8. The ventilation section 10 is connected to an exhaust port 14 provided at the center of the rotating shaft 12 through an opening 13 provided at a lower portion of the holding body 11. This ventilation path 12 is connected to a pressure reducing mechanism 15.

A carbon electrode 16 for arc discharge is provided on an upper portion facing the inner member 9.

Therefore, in order to manufacture a crucible using the manufacturing apparatus 7, the crucible forming die 8 is rotated at a high speed by operating a rotary drive source (not shown) and rotating the rotating shaft 12 in the direction of the arrow. I do. A supply pipe (not shown) supplies high-purity quartz powder into the crucible-forming mold 8 from above.
The supplied quartz powder is converted into a crucible mold 8 by centrifugal force.
Is formed as a crucible-shaped quartz-filled layer 17 pressed against the inner surface 2.

Further, in the atmosphere, the carbon electrode 16 is energized almost simultaneously with the pressure reduction by the operation of the pressure reduction mechanism 15 to heat the inside of the quartz filling layer 17.

The heating of the quartz-filled layer 17 by the carbon electrode 16 causes the quartz-filled layer 17 to be sequentially melted from the inside, but forms a substantially bubble-free transparent layer of only small bubbles on the inner surface 2. Then, an opaque layer 5 having a large number of bubbles is formed on the outer surface 4 to manufacture the quartz glass crucible 1 having a double-layer structure.

In the manufacturing process of the quartz glass crucible 1, in order to give the transparent layer 3 of the quartz glass crucible 1 a compressive stress that is half the breaking strength of the quartz glass crucible, the inner surface 2 must be cooled during cooling. This is performed by quenching from the outer surface 4.

That is, the following manufacturing conditions are set. Immediately after the completion of heating by the carbon electrode 16, an inert gas such as nitrogen, helium, or argon, for example, nitrogen, flows into the inner surface side 2 of the quartz glass crucible 1 for 100 to 300 liters / minute, for example, 100 liters / minute, for 5 to 10 minutes, for example, for 5 minutes. I do.

If the pressure is less than 100 liters / minute for 5 minutes, sufficient compressive strength cannot be obtained. If the pressure exceeds 300 liters / minute for 10 minutes, the compressive strength becomes excessive.

By manufacturing the quartz glass crucible 1 under the manufacturing conditions as described above, the quartz glass crucible 1 having a compressive stress that is half the breaking strength of the opaque layer 5 in the transparent layer 3 can be manufactured. .

In order to pull up the silicon single crystal 6 using the quartz glass crucible 1 according to the present invention, the nugget-like polysilicon is put into the quartz crucible 1, the heater 19 is energized to heat the quartz crucible 1, and the motor is heated. To rotate the rotating shaft 20 connected to the motor to rotate the quartz crucible 1.

After a certain time has passed and the nugget-like polysilicon has become the silicon melt 6, the seed shaft 21 is lowered,
The seed crystal 22 is brought into contact with the liquid surface of the silicon melt 6 to pull up the silicon single crystal 18.

At this time, in the silicon single crystal pulling step, since no large bubbles exist in the transparent layer 3 of the quartz glass crucible 1, the bubbles are dissolved together with the dissolution of the transparent layer 3 on the inner surface side 2 of the quartz glass crucible 1. There is no mixing in the melt 6 and no decrease in the DF ratio.

Further, since the transparent layer 3 has a compressive stress that is one half of the breaking strength of the opaque layer 5, the tiny bubbles existing in the transparent layer 3 expand to become large bubbles, and as described above, the inside Silicon melt 6 along with dissolution of transparent layer 3 on front side 2
There is no mixing in. Further, since a compressive stress is present in the transparent layer 3, the bubbles in the opaque layer 5 do not expand and expand and cleave toward the transparent layer 3 to adversely affect the growth of the silicon single crystal 18.

[0039]

EXAMPLE A quartz glass crucible was manufactured and an actual machine test of pulling a silicon single crystal was performed using the crucible.

(1) Manufacture of quartz glass crucible for test A natural quartz crystal was crushed and refined to produce an average particle diameter of 230 μm.
Quartz particles having a diameter of m were filled into a mold having a crucible size of 350 mm in outer diameter and 300 mm in height to have a deposited layer thickness of 20 mm.
From the outer surface side of the filled crucible type, 300
While reducing the pressure to a melting pressure of Torr, arc discharge was performed by a carbon electrode located above the inner surface side to melt the quartz particles.

The thickness of the molten layer is 12 mm (the transparent layer is about 2 m
m, the opaque layer is about 10 mm).
Adjusted for ~ 20 minutes. In a vacuum system of 500 Torr or less, a valve was provided to perform melting while controlling the pressure of the melting portion.

After heating by the arc discharge, the discharge is stopped,
Nitrogen gas is introduced into the quartz glass crucible inner surface area, and the inflow speed and time of the nitrogen gas are adjusted to obtain predetermined transparent layer thickness, opaque layer thickness, transparent layer breaking strength, and the like as shown in Table 1.
Further, a quartz gas crucible having a compressive stress of the transparent layer was manufactured (Example 4).

Also, the flow rate and time of the nitrogen gas were adjusted variously to produce quartz gas crucibles having various transparent layers, opaque layer thicknesses, opaque layer breaking strengths, and transparent layer compressive stresses as shown in Table 1. (Examples 1 to 3 and Comparative Example 1
~ 3).

(2) Measurement of Breaking Strength and Compressive Stress Preparation of Samples Samples for Breaking Strength: Only the opaque layer was cut out from the quartz glass crucibles of Examples 1-4 and Comparative Examples 1-3 produced by the above-mentioned production method. Each sample was prepared. -Compressive stress sample: Samples having a shape as shown in Fig. 4 were cut out from the quartz glass crucibles of Examples 1 to 4 and Comparative Examples 1 to 3 to produce them.

Measurement method: The breaking strength of the opaque layer was measured according to JIS standard R-1606.
(Fine ceramics room temperature and high temperature tensile strength test method). For the compressive stress of the transparent layer, a sample (crucible section) as shown in FIG. 4 described above is prepared, and a precision strain meter (manufactured by Toshiba Glass Co., Ltd .; SVP-30-II].

(3) Pull-up test on actual machine The quartz glass crucibles produced in (1), Examples 1-4,
Using Comparative Examples 1 to 3, a silicon single crystal was actually pulled by the above-described silicon single crystal pulling method, and DF
The rate was measured.

(4) Results of Measurement of Breaking Strength, Compressive Stress and Pull-Up Test of Actual Machine
Shown in

[0048]

[Table 1]

Results of Measurement of Layer Thickness, Breaking Strength of Opaque Layer, and Compressive Stress of Transparent Layer The DF ratios of Examples 1 to 4 were all higher than 94%,
In particular, it reaches 96% in the third embodiment and 97% in the fourth embodiment.

In Comparative Example 1, the thickness of the transparent layer was 7 mm, which is 70% of the thickness of the opaque layer, which is 70%, which exceeds the preferred range of 60%. Was insufficient, and the crucible was broken during pulling of the single crystal, and the pulling was interrupted.

In Comparative Example 2, the compressive stress of the transparent layer was 9 MPa, which was 25.7% of the breaking strength of the opaque layer of 35 MPa, and the bubbles in the transparent layer or the bubbles generated from the bubble nuclei were mixed into the silicon melt. The DF ratio was 90%, which was inferior to each of the examples, because the air bubbles in the opaque layer expanded and expanded toward the transparent layer, and the DF ratio was reduced.

In Comparative Example 3, the compressive stress of the transparent layer was 20 MPa.
The fracture strength of the opaque layer was 57.1% with respect to 35 MPa, and the crucible was destroyed by the thermal stress applied to the crucible and the load on the molten silicon loaded in the crucible, and the test was interrupted.

[0053]

According to the present invention, the transparent layer of the quartz glass crucible has a compressive stress of one half of the breaking strength of the quartz glass crucible.
The tiny bubbles existing in the transparent layer expand and become large bubbles, dissolving the transparent layer on the inner surface and suppressing the mixing of the bubbles into the silicon melt, and the bubbles in the opaque layer expand and expand toward the transparent layer. It is possible to provide a quartz glass crucible capable of obtaining a high single crystallization ratio without being cleaved and adversely affecting the growth of a silicon single crystal, and a method for manufacturing the same.

[Brief description of the drawings]

FIG. 1 is a sectional view of a quartz glass crucible according to the present invention.

FIG. 2 is a conceptual diagram of a manufacturing apparatus for a quartz glass crucible used in the method for manufacturing a quartz glass crucible according to the present invention.

FIG. 3 is an explanatory view of a silicon single crystal pulling apparatus using a quartz glass crucible according to the present invention.

FIG. 4 is an explanatory view of a sample for a compression stress measurement test.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Quartz glass crucible 2 Inner side 3 Transparent layer 4 Outer side 5 Opaque layer 6 Fused silicon 7 Manufacturing equipment 8 Crucible mold 9 Inner member 10 Vent section 11 Holder 12 Rotary shaft 13 Opening 14 Exhaust port 15 Decompression mechanism 16 Carbon Electrode 17 Quartz filling layer 18 Silicon single crystal 19 Heater 20 Rotation axis 21 Seed axis 22 Seed crystal

Claims (6)

[Claims] 1. A quartz glass crucible having a transparent layer on an inner surface side and an opaque layer having a large number of bubbles around the transparent layer, wherein the transparent layer is broken by the transparent layer. A quartz glass crucible for pulling a silicon single crystal, having a compressive stress of 30 to 50% of the strength. 2. The opaque layer has a breaking strength of 32 to 38 M.
The quartz glass crucible for pulling a silicon single crystal according to claim 1, wherein the pressure is Pa. 3. The thickness of the transparent layer is at least 1 mm, and the thickness of the transparent layer is 60% of the thickness of the opaque layer.
The quartz glass crucible for pulling a silicon single crystal according to claim 1, wherein: 4. A method for producing a quartz glass crucible for pulling a silicon single crystal, comprising preparing a crucible mold filled with quartz powder in a crucible-like body and heating the quartz powder from the inner side of the crucible-like body. A method for producing a quartz glass crucible for pulling a silicon single crystal, wherein cooling conditions are changed between an inner surface side and an outer surface side of the quartz glass crucible after heating the crucible mold. 5. The silicon single crystal pulling apparatus according to claim 4, wherein after the heating of the quartz powder, an inert gas is caused to flow into an inner surface side region of the quartz glass crucible and forcedly cooled from the inner surface side. A method for manufacturing a quartz glass crucible. 6. An inert gas inflow speed of 100 to 3
00 liter / minute and the forced cooling time is 5
The method for producing a quartz glass crucible for pulling a silicon single crystal according to claim 5, wherein the cooling is performed for 10 minutes, and then the mixture is left to cool.